1. Field of the Invention
The present invention relates to a fan unit having a fan which is used for forced air cooling of a desired equipment and performing predetermined processing for the temperature of an exterior or a predetermined place of the equipment to output the result of the processing; a motherboard provided on the rear face of a shelf or a rack on which the fan unit is disposed, with its wiring between the fan unit and a predetermined unit being formed as a wiring pattern; and an electronic equipment in which a plurality of the above-described fan units are provided and which is forcedly air-cooled by the fan units.
2. Description of the Related Art
In recent years, electronic equipments such as communication equipments and others have been low-priced and downsized and forced air cooling is applied to nodes adaptable to a wavelength-division multiplexing transmission system since precise temperature control and high-density mounting are severely demanded particularly for these nodes.
FIG. 10 is a view showing a structure example of a node to which the forced air cooling is applied.
In FIG. 10, shelves 102-1 and 102-2 are formed in a frame 101, and in slots in the shelves 102-1 and 102-2, packages 103-101 to 103-113 and 103-21 to 103-29 which operate based on predetermined functional distribution and load distribution are mounted respectively. In the upper part of the shelf 102-1 disposed are fan units 104-11 to 104-13, while in the lower part of the shelf 102-2 fan units 104-21 to 104-23 are disposed.
In the node as structured above, the fan units 104-11 to 104-13 and 104-21 to 104-23 are driven by the power supply steadily given thereto and the fan units 104-21 to 104-23 out of these fan units 104-11 to 104-13 and 104-21 to 104-23 blow air of an exterior of the frame 101 into the frame 101 (the shelves 102-1 and 102-2 (FIG. 10(a)).
The air thus blown in is warmed by heat generated in the packages 103-101 to 103-113 and 103-21 to 103-29 inside the frame 101 (the shelves 102-1 and 102-2) (FIG. 10(b)) and is radiated outside the frame 101 by the fan units 104-11 to 104-13 (FIG. 10(c)).
Therefore, highly reliable and stable forced air cooling is conducted for the packages 103-101 to 103-113 and 103-21 to 103-29 as long as the sum total of physical air quantities generated by the fan units 104-11 to 104-13 and 104-21 to 104-23 is sufficient.
Furthermore, all of the fan units 104-11 to 104-13 and 104-21 to 104-23 are structured as modules which are attachable and detachable via an identical connector, and therefore, the structure thereof is standardized and the number of spared components to be secured in the process of maintenance and operation is reduced.
Incidentally, in the above-described conventional example, the revolving speed of fans which are provided individually in the fan units 104-11 to 104-13 and 104-21 to 104-23 is set in advance at a value which enables radiation of a heat quantity larger than a ratio of the maximum heat quantity which is possible to be generated in all the packages 103-101 to 103-113 and 103-21 to 103-29, which are possible subjects of the forced air cooling, to the minimum number of the fan units which are possible to operate in parallel.
Consequently, the sum total of the air quantities of the fans which are provided in these fan units 104-11 to 104-13 and 104-21 to 104-23 secures sufficient allowance for calorific values of the packages 103-101 to 103-113 and 103-21 to 103-29, but it is often excessive.
Moreover, since physical moving mechanisms are provided in these fans, they have low reliability compared with electronic components and packages and make uselessly high level of noises even when power consumption by the packages 103-101 to 103-113 and 103-21 to 103-29 is small.
Consequently, not only reliability but also working environments in station offices have been degraded and restrictions on reduction in running cost have been caused.
Furthermore, when the fan units 104-11 to 104-13 and 104-21 to 104-23 are individually provided with temperature sensors and they independently vary the revolving speeds of their fans according to temperatures detected by the temperature sensors, the fan units 104-11 to 104-13 out of these fan units 104-11 to 104-13 and 104-21 to 104-23 independently increase the revolving speeds of their fans since the temperatures in these units are increased due to the heat radiated by the packages which are positioned under these units respectively.
However, even when the revolving speeds of a part of the fans are thus increased, an appropriate air quantity is not always obtainable unless the temperature sensors provided in the other fan units detect the aforesaid increase in temperature in parallel to increase the revolving speeds of the individual fans, and in addition, there is a high possibility that power supply is uselessly consumed by the plurality of fans.
Incidentally, the lack of the air quantity and the power consumption as mentioned above are avoidable by providing the following temperature sensor and control unit.                a temperature sensor for individually measuring the temperature of a desired place        a control unit which is structured separately from the fan units 104-11 to 104-13 and 104-21 to 104-23 and which plays a leading role in setting the revolving speed of the fans individually provided in these fan units 104-11 to 104-13 and 104-21 to 104-23 at a value suitable for the combinations of these temperatures        
However, the control unit as described above is complicated in its structure and large in its hardware scale, which is a factor to prevent a node from improving its total reliability and being downsized, and therefore, it has been difficult to apply the control unit in actual use.